Cosmology with Galaxy bias

Transcription

1 Cosmology with Galaxy bias Enrique Gaztañaga, M.Eriksen (PhD in progress...)

2 Figure of Merit (FoM): Expansion x Growth w(z) -> Expansion History (background metric) we will use w0 and wa γ -> Growth History (metric perturbations) probably need one more parameter here δ = Hθ Linear Theory: P(k,z) ~D 2 (z) P(k,0) + mass conservation Is this the best choice for 3 parameters? θ = f(ω) δ f = Velocity growth factor: tell us if gravity is really responsible for structure formation! Could also tell us about cosmological parameters or Modify Gravity 1 = σ(w0) σ(wa) σ(γ) Om - ODE - h - sig8 - Ob - w0 - wa -γ- ns - bias(z) need clustering

3 The role of Galaxy Bias Search of Cosmological parameters is hinder by BIAS! Options: A) Avoid BIAS: BAO, SNe, Cluster counts, WL and through away most information B) Understand Bias <==> Galaxy Formation Xtalk probes: combine different probes to measure bias together with other cosmological parameters

4 Workshop on Galaxy Bias: Non-linear, Non-local and Non-Gaussian here bias is: Linear and local Deterministic: r=1 Gaussian IC on linear scales: b(z, type) as a function of redshift (one bias per z-bin) and type first step (better than non!)

5 XTalks in Galaxy Clustering astro- ph: Galaxy Clustering (real) 2pt: 3D, lots of info but degenerate with bias: can measure linear shape, but not growth 2. Galaxy Clustering 3pt: 3D (break degeneracy?) 3. Weak Lensing: 2D (unbiased but degenerate & few 2D modes) 4. Redshift Space Distortions (can be used in to measure bias but 1D) 5. BAO: (unbiased but 1.5D) Combine probes: RSD + WL Cross-correlate probes: galaxy-lensing Combine Photometric & Spectroscopic Survey: sampling variance, photo-z accuracy

6 Photometric Sample (F) i ~ 24 2D weak lensing Δz = 0.03 FxB 100 Mpc/h 10000Km/s use WL & RSD to measure bias recover full 3D dm info Δz = Spectroscopic Sample (B) i ~ Mpc/h 1000Km/s

7 Anna Cabré s PhD Thesis arxiv: Crocce etal 2011 DR7 Errors from MICE sim 19 BAO: radial H(z) H(z=0.34) = 83.8 ±3.0± 1.6 EG, Cabre & Hui (2009) Transverse cdz/h(z) θ(z=0.34) = 3.90 ± 0.38 Carnero etal 2011

8 RSD in 2D Jacobo Asorey & MarOn Crocce arxiv: Adjacent bins (no photo- z outliers) 8

9 Martin Eriksen RSD and BAO in cross-correlations RSD in correlations. Text

10 RSD+WL: Same or different sky? Same Sky: factor of 2 less Area! but note that covariance <WLxRSD> ~ 0 while <FF BB> 0 Different Sky: no cross-correlations & no Covariance (smaller sampling variance, but no sampling variance cancelation) 1. Gaztanaga E., Eriksen M., Crocce M., Castander F. J.,Fosalba P., Marti P., Miquel R., Cabre A., astro- ph: Cai Y.-C., Bernstein G., astro- ph: Kirk D., Lahav O., Bridle S., Jouvel S., Abdalla F. B., Frieman J. A., astro- ph: Font-Ribera A., McDonald P., Mostek N., Reid B. A., Seo H.-J., Slosar A., astro- ph: de Putter R., Dore O., Takada M., astro- ph: D+3D Cov ~ 0 <g F g B > 0 2D, narrow bins, Limber FxB >> F+B 2 2D+3D Cov~ 0 <g F g B >=0 FxB > F+B 3 2D Cov 0 <g F g B >=0, no Limber FxB >> F+B 4 2D+3D Cov ~ 0 <g F g B > 0 2D, nl BAO FxB ~ F+B 5 2D+3D Cov ~ 0 <g F g B > 0 2D, nl BAO FxB ~ F+B 10

11 Forecast WL+RSD Nuisance parameters: one bias per z-bin & pop, photo-z transitions (rij, can be measured), noise (σ/n) Cosmological: Om - ODE - h - sig8 - Ob - w0 - wa - γ - ns - bias(z) shear-shear (2D):! <γ γ> galaxy-shear (2D need narrow bins) galaxy-galaxy (3D or narrow bins): <g γ> <g g> including BAO, RSD and WL magnification F= Faint (Photometric dz~0.05) sample: <γ F γ F >, <g F γ F >, <g F g F > B= Bright (Spectroscopic dz~0.003) sample: <γ B γ B >, <g B γ B >, <g B g B > F+B= No overlap => no cross <FB>=0 & no Covariance : <FF BB>=0 FxB= Overlaping => <FB> 0 & <FF BB> 0 11

12 New Forecast based on Exact calculavon with narrow 2D z- bins Martin Eriksen 12

13 Adding crosscorrelation between redshifts FoM increases as we add more cross-correlations zi-zj <Δz due to RSD and WL WL FoMωγ with shear Same sky (FxB) RSD without shear Martin Eriksen zi-zj < Δz max

14 Our new Exact Calculation Forecast: Martin Eriksen sq.deg. WLxG*+RSD+BAO (cross Cl: l<300 + Planck priors) F Photometric (DES iab<24) B Spectroscopic (PAU iab<22.5) F+B Combine both as Independent 2.6 / fix bias 38 no lens 0.03 /no BAO 2.0/no RSD / fix bias 44 no lens 4.1 /no BAO 4.3/no RSD / fix bias 157 no lens 4.7 /no BAO 13/no RSD 9 FxB CrossCorrelated over same Area *WLxG: shear-shear, galaxy-shear, galaxy-galaxy (including MAG) 32 /fix bias 189 no lens 5.9 /no BAO 22/no RSD 15 no cross FB: 26! FxB (no cross) > F+B

15 Martin Eriksen with shear Same sky (FxB)

16 Martin Eriksen without shear Same sky (FxB)

17 Error in bias for <FB>=0 (without cross-correlation) Compare cases: <FF BB>=0 with <FF BB> 0 (same sky) ratio relative to the case <FB> 0 and <FF BB> 0 <FF BB>=0 <FF BB>=0 Bright <FF BB>=0 Faint <FF BB> 0 Bright <FF BB> 0 Faint Including Covariance Reduces Error in F bias (but not in B bias) <FF BB> 0 Including Cross-correlation Reduces Error in F & B bias

18 Implications for Bias: Several ways to constrain a simple linear bias model: WL, RSD Can use 2D cross-correlations to combine (3D) RSD with WL Cross-correlations <FB> improve bias measurements (and FoM) F and B populations can reduce cosmic variance (RSD and ratio bias) F linear bias (from WL and counts) is better constrained, but B sample provide better FoM. The combination is best over the same sky. FoM (when bias is known) can be ~100 better than BAO or WL! Low radial accuracy (~20Mpc/h) for linear scales => PAU photo-z

19 THE END thank you! 19